tracing: Enable snapshot when any latency tracer is enabled

The snapshot utility is extremely useful, and does not add any more
overhead in memory when another latency tracer is enabled. They use
the snapshot underneath. There's no reason to hide the snapshot file
when a latency tracer has been enabled in the kernel.

If any of the latency tracers (irq, preempt or wakeup) is enabled
then also select the snapshot facility.

Note, snapshot can be enabled without the latency tracers enabled.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/Kconfig b/kernel/trace/Kconfig
index b516a8e..590a27f 100644 (file)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -191,6 +191,7 @@ config IRQSOFF_TRACER
        select GENERIC_TRACER
        select TRACER_MAX_TRACE
        select RING_BUFFER_ALLOW_SWAP
+       select TRACER_SNAPSHOT
        help
          This option measures the time spent in irqs-off critical
          sections, with microsecond accuracy.
@@ -213,6 +214,7 @@ config PREEMPT_TRACER
        select GENERIC_TRACER
        select TRACER_MAX_TRACE
        select RING_BUFFER_ALLOW_SWAP
+       select TRACER_SNAPSHOT
        help
          This option measures the time spent in preemption-off critical
          sections, with microsecond accuracy.
@@ -232,6 +234,7 @@ config SCHED_TRACER
        select GENERIC_TRACER
        select CONTEXT_SWITCH_TRACER
        select TRACER_MAX_TRACE
+       select TRACER_SNAPSHOT
        help
          This tracer tracks the latency of the highest priority task
          to be scheduled in, starting from the point it has woken up.